Patellar (kneecap) dislocations occur with significant regularity, especially in younger athletes. Most of the dislocations occur laterally (outside). When these occur, they are associated with significant pain and swelling. Following a patellar dislocation, the first step must be to relocate the patella into the trochlear groove. This often happens spontaneously as the individual extends the knee either while still on the field of play or in an emergency room or training room as the knee is extended for examination. Occasionally relocation of the patella occurs spontaneously before examination and its occurrence must be inferred by finding related problems.
Associated problems normally occur with patellar dislocations, the most obvious of which is tearing of the ligaments that stabilize the kneecap itself. As is the case with all other joints, ligamentous disruption or tearing occurs to allow the joint to dislocate. In the case of patellar dislocation, the ligaments on the inside of the knee are the most commonly injured as the kneecap slides laterally. While tearing of these ligaments is unfortunate, they do have the potential to heal. Of much more concern, are the small fragments of cartilage and bone that often are knocked off of the kneecap or the lateral femoral condyle during the relocation of the kneecap. These fragments become loose bodies and usually require removal during an arthroscopic procedure. Patellar dislocations can cause significant quadriceps muscle injuries, which can be made worse due to the effusion within the knee or to early onset of exercises and premature return to play.
A condition referred to as patellar subluxation also exists. The problem exists on a continuum between patellofemoral malalignment and patellar dislocation. It can be sequelae of a traumatic dislocation or in situations where patellar hyperlaxity exists. A subluxation is a partial dislocation in which the patella attempts to dislocate but does not do so completely. Situations such as these are very disconcerting and often give the patients a sense of giving way or buckling. At a minimum, these situations should be treated with aggressive therapeutic intervention as the constant subluxation events not only will interfere with competition, but will also potentially cause repeated wear and discomfort within the patellofemoral joint.
Patellar dislocations can occur either in contact or non-contact situations. An athlete can dislocate his/her patella when the foot is planted and a rapid change of direction or twisting occurs. Usually a pre-existence ligamentous laxity is required to allow a dislocation to occur in this manner. Direct blows to a knee can cause dislocations as well. The force of these is obviously much greater and usually causes more severe damage especially to restraining ligaments.
- Rapid, acute swelling.
- Extreme pain initially until relocation occurs.
- Continued pain along medial (inside) ligaments.
- Discoloration medially at site of ligament injury.
- Sense of instability and apprehension that problem will recur.
Normal care of patellar dislocations, when a loose fragment has not been created is the immobilization of the knee for a short period of time (seven to 10 days). During this time, the swelling is reduced and the acute discomfort of the dislocation decreases. Slow mobilization of the knee and of the patellofemoral joint is then begun, and usually full recovery can be expected within a three to six week period. This period of time is significantly lengthened when the patellar dislocation is recurrent.
Unfortunately, once a patellar dislocation occurs, especially when it occurs in a situation where hyperlaxity of the ligaments exists, which is commonly the case, recurrent dislocations can be expected. These are significantly problematic for athletes as they often come in the midst of the season. Conservative management of these problems in season with appropriate rest, appropriate hip and thigh muscle strengthening, and perhaps the use of a patellar buttress brace is appropriate.
Alternative Treatment Options
Some situations of patellar dislocation can and/or should be treated surgically. One situation is when recurrent dislocations occur. In these situations, to limit the amount of lost time in competition and to reduce the chances for cartilage lesions on the undersurface of the patella, which often are non-reparable, patellar stabilization procedures are appropriate. These procedures can be either soft tissue or bone procedures, or a combination thereof. First-time traumatic patellar dislocations can also be treated with procedures such as this, and in chosen situations doing so may be appropriate.
It has been found in retrospective studies that the incidence of recurrent dislocation after the first dislocation occurs can be as high as 40 percent. Surgically treating those dislocations by lessening lateral tension and tightening medial restraint could reduce this recurrence rate to below 10 percent.
Surgical procedures on the patella are usually done in the out-patient setting. Procedures limited to altering soft-tissue tension begin rehabilitation within a week and return to activity can be expected as early as six weeks. Procedures that require bone work (osteotomies) require a period of relative immobilization and need 10 to 12 weeks before a return to athletic activity is permitted.